py: Support single argument to optimised MP_OBJ_STOP_ITERATION.

The MP_OBJ_STOP_ITERATION optimisation is a shortcut for creating a
StopIteration() exception object, and means that heap memory does not need
to be allocated for the exception (in cases where it can be used).  This
commit allows this optimised object to take an optional argument (before,
it could only have no argument).

The commit also adds some new tests to cover corner cases with
StopIteration and generators that previously did not work.

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 63 insertions, 0 deletions

diff --git a/tests/basics/stopiteration.py b/tests/basics/stopiteration.py
new file mode 100644
index 000000000..d4719c9bc
--- /dev/null
+++ b/tests/basics/stopiteration.py
@@ -0,0 +1,63 @@
+# test StopIteration interaction with generators
+
+try:
+    enumerate, exec
+except:
+    print("SKIP")
+    raise SystemExit
+
+
+def get_stop_iter_arg(msg, code):
+    try:
+        exec(code)
+        print("FAIL")
+    except StopIteration as er:
+        print(msg, er.args)
+
+
+class A:
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        raise StopIteration(42)
+
+
+class B:
+    def __getitem__(self, index):
+        # argument to StopIteration should get ignored
+        raise StopIteration(42)
+
+
+def gen(x):
+    return x
+    yield
+
+
+def gen2(x):
+    try:
+        yield
+    except ValueError:
+        pass
+    return x
+
+
+get_stop_iter_arg("next", "next(A())")
+get_stop_iter_arg("iter", "next(iter(B()))")
+get_stop_iter_arg("enumerate", "next(enumerate(A()))")
+get_stop_iter_arg("map", "next(map(lambda x:x, A()))")
+get_stop_iter_arg("zip", "next(zip(A()))")
+g = gen(None)
+get_stop_iter_arg("generator0", "next(g)")
+get_stop_iter_arg("generator1", "next(g)")
+g = gen(42)
+get_stop_iter_arg("generator0", "next(g)")
+get_stop_iter_arg("generator1", "next(g)")
+get_stop_iter_arg("send", "gen(None).send(None)")
+get_stop_iter_arg("send", "gen(42).send(None)")
+g = gen2(None)
+next(g)
+get_stop_iter_arg("throw", "g.throw(ValueError)")
+g = gen2(42)
+next(g)
+get_stop_iter_arg("throw", "g.throw(ValueError)")